1. Field of the Invention
The present invention relates to a crimping terminal.
2. Description of the Related Art
As a crimping terminal for an electrical equipment system of an automobile, for example, a crimping terminal of an open barrel type having a conductor crimping portion with substantially a U-shaped cross section has been used. Generally, for caulking this kind of crimping terminal, caulking referred to as B crimp is performed (refer to Japanese Patent Application Laid-open Nos. 2011-96451 and 2011-96452).
As illustrated in FIG. 6, a crimping terminal 501 on which the B crimp is performed includes an electrical connecting portion 507 to be connected to a mating connector, at a front portion in a longitudinal direction of the terminal (that is, a longitudinal direction of a conductor 505 of an electric wire 503 to be connected; refer to FIGS. 7A and 7B). At a rear portion in a longitudinal direction of the terminal, continuing to the electrical connecting portion 507, a conductor crimping portion 509 is provided, which is to be caulked to the conductor 505 that is exposed at a distal end of the electric wire 503. At a further rear portion, provided is a sheath caulking portion 511 to be caulked from the outside of an insulating sheath of the electric wire 503.
The conductor crimping portion 509 is configured to have a substantially U-shaped cross section, together with a base plate portion 513, and with a pair of conductor caulking pieces 515 extending upwardly from both left and right both edges in the longitudinal direction of the base plate portion 513. The pair of conductor caulking pieces 515 are caulked so as to wrap the conductor 505 of the electric wire 503, the conductor 505 being disposed on an inner surface of the base plate portion 513 (refer to FIG. 7A).
When crimping the conductor crimping portion 509 of the crimping terminal 501 to the conductor 505 at the distal end of the electric wire 503, the crimping terminal 501 is disposed on a placement surface (upper surface) of a lower mold (anvil) (not illustrated). Subsequently, the conductor 505 at the distal end of the electric wire 503 is inserted between the pair of conductor caulking pieces 515 of the conductor crimping portion 509, to be disposed on the inner surface of the base plate portion 513. Then, by moving an upper mold (crimper) downwardly relative to the lower mold, the leading end sides of the conductor caulking pieces 515 are gradually folded inwardly at a guide slope of the upper mold.
Then, by further moving the upper mold downwardly relative to the lower mold, the leading ends of the conductor caulking pieces 515 are finally rounded so as to be folded back toward the conductor 505 side on a curved surface ranging from the guide slope of the upper mold to a central angled portion (refer to FIG. 7A). The leading ends of the conductor caulking pieces 515 are bitten into the conductor 505 while being rubbed with each other. With this, the conductor crimping portion 509 comes to be the B crimp in which the pair of conductor caulking pieces 515 have been used to caulk the conductor 505 so as to wrap it to form a B shape (refer to FIG. 7A).
The previously-mentioned B crimp, however is likely to cause infiltration of water from a seam joining portion 517, leading to possible corrosion of the conductor 505. When an aluminum electric wire is used, in particular, an oxide film generated due to corrosion has an insulating property, leading to an increased electric resistance and lowered electrical reliability. Accordingly, when an aluminum electric wire is used, in particular, it is proposed to use, as a form of caulking illustrated in FIG. 7B, an overlap crimping as a countermeasure, in which caulking is performed such that one of the pair of the conductor caulking pieces 515 comes at a lower side, the other overlapping an upper side of the one of the pair, in order to delay the infiltration of water (refer to Japanese Patent Application Laid-open No. 2009-152053).
The overlap crimping, however, compared to the B crimp, has a larger spring back on the conductor caulking pieces 515 at the time of crimping, as illustrated in arrow a direction in FIG. 7B. As a result, it is likely to cause a decrease in a caulking force at the conductor crimping portion 509, leading to a decrease in fixing strength, or a decrease in crimping performance such as a rise in electric resistance. Furthermore, overlap crimping has low rigidity in a caulking portion, leading to an occurrence of a gap S at on an overlapping surface, as illustrated in FIG. 7B, in response to the ambient temperature changes. For these reasons, it is desired to supply an overlap crimping with further improved electrical reliability.